I had thought he would be nervous in this speech competition but he turned out to be

问题补充：

--- I had thought he would be nervous in this speech competition, but he turned out to be calm.

--- He quite enough preparation for it.

A. should do

B. must do

C. should have done

D. must have done

答案：

A. should do

B. must do

C. should have done

(答案→)D. must have done

解析：考查情态动词。句意：——我本以为他在演讲比赛中会紧张，但结果他很平静。——他一定是准备得相当充分。must+ have done表示对过去的肯定的推测，意思是“肯定”，should have done 本应该做某事而实际没做。